A semiconductor device is typically packaged as a chip and mounted on a circuit board to mechanically and electrically connect the semiconductor device to the circuit board. This allows semiconductor device to be electrically connected to various other electrical devices within a digital data processing system.
One known package type is a surface vertical package ("SVP"), which provides for the edge-mounting of chips to circuit boards. The semiconductor device is packaged in a relatively flat package such that the leads that provide for electrical connections to the semiconductor device are positioned on one edge of the chip. Each lead of the SVP chip may be soldered to a respective solder pad on a circuit board to mechanically and electrically connect the semiconductor device to the circuit board. The leads of the SVP chip are bent substantially perpendicular relative to the SVP package so that the SVP chip may be placed upright over the circuit board in soldering each lead to its respective solder pad. The SVP chip may have at its bottom edge supporting pins, for example, to help the SVP chip stand upright in soldering the SVP chip to the circuit board.
In soldering the SVP chip to the circuit board the SVP chip may nevertheless fall over, for example by the mechanical movement of the circuit board through a solder oven, and thus have to be resoldered to the circuit board. Even after soldering the SVP chip to the circuit board, the electrical connection between the SVP chip and the circuit board must be tested to ensure that each lead of the SVP chip has been properly aligned with and soldered to its respective solder pad on the circuit board. If the SVP chip has not been suitably soldered to the circuit board, the SVP chip must be resoldered.
Furthermore, the solder connection between the SVP chip and the circuit board may deteriorate during the life of the circuit board, for example by being subjected to various mechanical stresses. Typical users may not have the equipment or know-how to resolder a SVP chip to the circuit board and subsequently test the resulting electrical connection. Thus, a user could be inconvenienced and subjected to the cost of having to replace the circuit board or having someone else resolder a SVP chip to the circuit board.
Another known package type is a surface horizontal package ("SHP"), which provides for the horizontal mounting of an integrated circuit chip to the circuit board. The integrated circuit is mounted inside a thin plastic package of the SHP and connected to metal leads residing on one of the four of the thin sides of the plastic package of the SHP. The SHP chip has pins on an opposite side of the plastic package for aligning and mounting the chip. The metal leads of the SHP are soldered to metallic lines on a circuit board.
The connection of an SHP chip to a circuit board shares some of the same problems as the connection of an SVP chip to a circuit board. Leads of the SHP can be difficult to properly solder. The electrical connection with respect to the soldered leads must be tested, and an SHP must be resoldered if the solder connection is defective. Moreover, even good soldered leads of the SHP can deteriorate over time.
Users of computers or other electrical systems are typically unable to expand the functionality of the system with the granularity of a single soldered SVP chip or soldered SHP chip in a relatively easy manner. Typical digital data processing systems with soldered SVP or SHP chips on circuit boards provide for user-expansion capabilities with the granularity of a circuit board, rather than of a chip. Only by adding, removing, or replacing an entire circuit board can the user easily add or remove the functionality of a single chip.